Production of ethylene oxide by catalytic gas-phase oxidation of ethylene with a molecular-oxygen-containing gas in the presence of a silver catalyst has been widely carried out industrially. As for the silver catalyst to be used in this catalytic gas-phase oxidation, various technologies have been proposed concerning carrier thereof, supporting method, kind and addition amount of reaction accelerator, and the like.
For example, by paying attention to catalyst component, a technology in which catalytic selectivity is improved by using an alkali metal and rhenium in combination as an accelerator has been disclosed (Patent Literatures 1 and 2). Patent Literature 1 discloses a catalyst composition for producing ethylene oxide, comprising rhenium/a compound thereof and other metal such as alkali metal/a compound thereof as a catalyst component, as well as a support having surface area less than 20 m2/g. In addition, Patent Literature 2 discloses a catalyst composition for producing ethylene oxide, comprising silver metal; rhenium, tungsten, molybdenum/a compound thereof; and a component in which a part of rubidium or cesium is substituted by potassium, which are deposited on a carrier having a surface area of 500 m2/kg or more.
On the other hand, by paying attention to a carrier in the catalysts using silver and rhenium as a catalyst component, a technology to improve activity and selectivity of catalyst has been disclosed (Patent Literature 3). In Patent Literature 3, attention is focused on a point that pores of carrier, in particular, characteristics of pore size distribution and pore volume resulting from pores having a pore size in a specified range play an important role, and there has been disclosed a catalyst comprising a carrier having at least 1 m2/g of surface area and such pore size distribution that pores having a diameter in a range of 0.2 μm to 10 μm corresponds to at least 70% of the total pore volume, and said pores give at least 0.27 ml/g of pore volume in total to the weight of the carrier; and silver deposited on the carrier in an amount of at least 10 g/kg to the weight of the catalyst.